PHP面向对象

<?php
class Point
{
    //静态成员，类内被使用self::$size，在类外Point::size
    static $size=10;
    //常量，使用时可以不用$
    const PI=301415926；
    //私有字段
    private $id;
    private $x;
    private $y;
    //使用自定义的方法进行访问控制
    function getId()
    {
        return $this->id;
    }
    //提供对私有字段的访问控制
    function __get($property_name)
    {
        if(isset($this->$property_name))
        {
            return $this->$property_name;
        }
        else
        {
            return NULL;
        }
    }
    //提供对私有字段的写入控制
    function __set($property_name,$value)
    {
        if(is_double($value))
        {
            $this->$property_name=value;
        }
        else
        {
            echo "error: value is not a double number.";
        }
    }
    //构造函数
    function __construct($x,$y,$id=0)
    {
        $this->x=$x;
        $this->y=$y;
        $this->id=$id;
    }
    function Print_info()
    {
        echo $this->id,"<br>";
        echo $this->x,"<br>";
        echo $this->y,"<br>";
    }

    //析构函数
    functionfunction __destruct()
    {
        echo "destruct function";
    }
}
?>

<?php
abstract class Object
{
    abstract public function Output();
    final public function Msg()
    {
        echo "object msg","<br>";
    }
}
final class Point extends Object
{
    public function Output()
    {
        //调用基类的方法,当然可以$this->Msg(),方法被覆盖时就不能用了吧！
        parent::Msg();
        echo "point","<br>";
    }
}
class Rectangle extends Object
{
    public function Output()
    {
        echo "Rectangle","<br>";
    }
}
//多态性，限制传入的类型为Object
function runObject(Object $obj)
{
    $obj->Output();
}
runObject(new Point());
runObject(new Rectangle());
?>

<?php
interface IUser
{
    public function addUser();
}
class Administrator implements IUser
{
    public function addUser()
    {
        echo "add user";
    }
}
(new Administrator())->addUser();
?>